Hanging Idle on R80 G/S

Discussion in 'Airheads' started by One Less Harley, Aug 8, 2012.

  1. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    When my bike is warmed up when closing the throttle, the bike just doesn't drop down to idle very quick, it hesitates for about 3-5 seconds then will idle. Cables aren't sticky, and I've pulled the carbs and double checked for throttle shaft freedom of movement, no stickiness what so ever. Also checked butterflies (readjusted one) for center to carb bore, all appears fine.......so is this an indication of stuck ignition advance weights or something else.
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  2. supershaft

    supershaft because I can

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    It can be. Although most every one advised to check them here on the net mostly for an old service bulletin that came out decades ago, I rarely ever see them stuck. Nine out of ten times it is a combo of idle speed adjustment and the mixture screw adjustment. The other one time is leaking carb spigots. Roughly speaking, of course.
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  3. hardwaregrrl

    hardwaregrrl ignore list

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    Richard, I had similar symptoms with the ST. Hanging idle especially coming off the hwy, cleaned and greased the weights, it would behave properly for another 100miles, bought a rebuilt can from Rick just for kicks. Never have had it hang since. ('08)
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  4. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    I've read to go richer on the Needle Jet ,but since it is an idle problem wouldn't it make since to go larger on the Idle Jet???

    1st check for air leaks, then possibly go to the next size larger Main Jet as I have 135's in there right now. Needle clip 2nd from top. Might be running a little lean. I've been having preignition issues for a while so this may be a symptom of running lean (?).

    Main Jet 135 (150 stock, 130 stock for 1981)
    Idle Jet 45 (45 stock for 1981,40 for 83-86)
    needle Jet 266 (stock) , needle has about 15,000 miles
    Needle clip 2nd from top (3rd stock)
    Needle 46-241 (46-251 for 1981)


    BTW-I'm very confidant that the idle mixture and sync are dead on. A hair rich on the idle screw to prevent off throttle hesitation.

    Don't want to blame the bean can just yet.
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  5. supershaft

    supershaft because I can

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    Was the bean can under water? Full of mud? They do stick but very rarely. Some people say they stick all the time because they are selling aftermarket ignitions with the exact same hall effects sensor that the bean can has. 99% of the time a bean can goes bad, it's the hall effect sensor. Since the aftermarket ignitions use the exact same technology, they trump up the mechanical advance failing. Ausherman has a "fool proof" method of diagnosing a stuck advance and it is anything but . . . . I am not saying they never stick. Anything is possible. I have worked on a lot of airheads and been around a lot of dealerships since the can first came out and I have been looking hard for sticking advances since that bulletin warning about sticking advances first came out around '85 (?). I almost never see it.

    It has nothing to do with your mains. Your mains are already too rich. Later on they leaned the mains to 135's. They run better, make more power and get better mileage with 135's.

    They run like crap with the jet needle on the 4th position. It richens the midrange way too much. What you might actually need richer (you will probably only hear here from me) are 268 needle jets. But still, that will hardly effect your fast idle.

    You don't need richer idle jets either.

    Now to what it is usually. How are you sure the mixture screw is dead on? :ear That has me suspicious right there. Do you mean half way between the stumbling points for each carb? If so, richen them up a bit from there. Were your stumbling points, for instance, 12 hours apart on one carb and six hours apart one the other? Richen the one up one hour and the other 30 minutes so to speak.

    If your bike idles fine cold with the choke off or even close to it, your idle speed is too high. Lower it a bit.

    Air leaks? Check the spigots when the engine is good and hot and fast idling. If brake cleaner effects engine speed, you have a leak there.

    There are other things that can cause fast idle but it is super rare in my experience. Check the timing and make sure it is on the S mark as well as the Z mark. Sometimes it isn't a sticking advance but rather the timing itself. Lots of times bean cans won't time idle and fast idle at the same time since new. That can be adjusted out by bending the weight stop tabs. Good luck! Maybe it IS a sticking advance but surely this advice can help somebody out there because it holds true ALL the time!
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  6. Bulldust

    Bulldust Bulldust

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    Yes sticking advance weights.
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  7. Prutser

    Prutser Long timer

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    Did you check the valve settings already? Had the problem many times on bikes with leaking or to tight valves !
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  8. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    I'll do a valve check while it's cold 1st. Half way between stumble point on the AF mixture screws, bike doesn't stumble when slightly cracking the throttle, like it had one time before. I'll richen the AF mixture a wee bit.

    Bike needs choke when cold and is a little hard to start when cold.

    P/n for the 268 ( P/N 13 11 1 260971)
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  9. JRP

    JRP Old guy

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    +1
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  10. Airhead Wrangler

    Airhead Wrangler Long timer

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    Stuck advance weights are probably the more common problem, but I had the same thing once and it was caused by a loose butterfly plate. When the throttle was open it would move off center and when I let off the throttle it would not close all the way, but after a few seconds the vibration of the engine would allow it to migrate back into place and close all the way. Likewise a couple chops of the throttle would center it up again. Looking through the carb it looked well centered in the bore, and in every way just fine until I opened the butterfly a bit and felt that it was wiggly. My first instinct was also advance weights which I lubed the hell out of with no effect. Strangely enough, the engine didn't sound wildly out of balance. It ran pretty smoothly, even when idling at 2000 rpm.
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  11. Boxer Metal

    Boxer Metal Mad Scientist

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    It's your advance in the bean can. There are those that stick a little bit now and those that will start to stick not to far in the future:D
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  12. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    As others have mentioned the idle does tapper off when letting the clutch drag.

    Did the valve adjustment, exhaust were a little tight. Doubled checked the carb jets and the main jet was a 135...which makes since as the bike has been very slow to warm up and have experienced that before with the 135's.

    I'll take it for a ride, but it's cool out today and will take some time to warmup fully. If it still hesitates the 142 mj or 145's are going in.

    Butterflies where double check for centering and tightness previously.

    I may and try to source out the 268 needle jet and possibly the other needle that's listed for the R80's.

    I want to make sure it's not the carbs, before looking into the bean can. If it winds up being the bean can then I'll probably buy Ricks and save the old one as back up. I did lube it a while back though.
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  13. Solo Lobo

    Solo Lobo airhead or nothing

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    Did you check that the choke's are fully returning and not hanging up a bit as well... just try and depress them fully down with a finger to see if there is any play
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  14. England-Kev

    England-Kev Long timer

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    +1, also try increasing the free play in the throttle cables at the carb end.
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  15. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    cables are slack
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  16. batoutoflahonda

    batoutoflahonda Long timer

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    I'm with the shaft on idle speed/mix screw. Went round and round on my bike with this. You really got to get it hot and then start making adjustments. It's a pretty fine line. I even grabbed a screw driver and was adjusting on the road then went home and fine tuned it. Helps and is kinda fun to pug in a small balancer like a twin max or morgan and take it down the road with it hooked up to see what's going on. Also helps to develop an ear for it if you're new to airheads.

    The Idle creeps up on bikes when they get hot. A lot of modern carberated bikes (My '07 CBR600RR for example, and all my dirt bikes) have a big old knob sticking out so you can tune it down/up. Even my fuel injected '01 BMW R1100S idle creeps up in traffic.

    All the idle issues went away on my bike with new pistons, rings, and valves/seats. They had recessed quite a bit and one of the exhaust valves had a hole in it. That was at 70k. So if you are really struggling with it and it won't hold a tune, and are uncertain of the health of the motor, maybe a quick compression check is in order.
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  17. photomd

    photomd Been here awhile

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    Have you checked your float level? Mine idle would hang a little as well as revs would stumble above about 80mph. My float level was too low. I had set it by the Haynes manual. After this site referred to Snowbum's settings, I set it at a measured 24mm and all it good. Could this be it? :ear
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  18. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    Rechecked sync..and it's very good w/ the twin max. Didn't get it quite hot enough, but will take the twin max with me next time and take for a long ride and hook it up. It will show if one carb is hanging open.

    Not fully HOT, and the idle hung a little high, maybe +100-200 RPM, might get worse when very hot. Next step will be to enrich the A/F mixture.
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  19. supershaft

    supershaft because I can

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    I forgot to mention the choke cables but I figured you had already checked them. Same with float level. That's carb check #1. I do find floats maladjusted all the time. It could be the throttle plate too but it is most usually carb adjustment. I fix it all the time.

    The main jets have almost nothing to do with it. Besides, main jets should absolutely not be picked for better warm up. :huh Leave the 135's in it!

    Very slow to warm up? That is a sign of a well jetted bike!! Carbs have chokes a reason! Remember? They are to get your bike started and through the warm up period because if your bike is jetted to for best performance when hot it will be jetted way to lean to run well when cold and just about impossible to start without a choke or the like.

    Source needle jets? The best place to get them is from a BMW dealer. Look up the PN and order them.

    The mixture screws very often need to be set an hour or so richer than the midway point in order to not fast idle and/or pop on decel.

    Idle speed? :ear I certainly hope you need choke to start the bike and get back out of it as fast as you can but what about the idle speed. It shouldn't idle at the speed you want it to idle at until you ride it for at least ten miles. Otherwise they will fast idle.

    I suspected we would here a lot about the sticking weights. I have worked on bean can bikes or been in the shop while they were getting worked on literally hundreds of times. I think the problem is largely hype started by that service bulletin and feed by people selling alternatives that need a sales angle since they are really selling the same technology that fails in the bean can.
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  20. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    I forgot to mention the choke cables but I figured you had already checked them. Same with float level. That's carb check #1. I do find floats maladjusted all the time. It could be the throttle plate too but it is most usually carb adjustment. I fix it all the time.

    My choke cables have seen better days and adjusters are screwed all the way down, may need to see if I have a new set laying around. They have very little slack in them. Pretty sure float level is ok as they were adjusted by me three years ago when purchased.



    Very slow to warm up? That is a sign of a well jetted bike!! Carbs have chokes a reason! Remember? They are to get your bike started and through the warm up period because if your bike is jetted to for best performance when hot it will be jetted way to lean to run well when cold and just about impossible to start without a choke or the like.

    Bike will not start easily w/o the choke and takes +/- 15 minutes to warm up and shut it off.

    Source needle jets? The best place to get them is from a BMW dealer


    Yeah, knew Bing was a waste of $$$$$, found the 268 by cross referencing the Chilton. Notice early R80 G/S list different needle and carb piston and spring..interesting.


    The mixture screws very often need to be set an hour or so richer than the midway point in order to not fast idle and/or pop on decel.

    This Is what's next, richen up A/F mix.

    Idle speed? :ear I certainly hope you need choke to start the bike and get back out of it as fast as you can but what about the idle speed. It shouldn't idle at the speed you want it to idle at until you ride it for at least ten miles. Otherwise they will fast idle.

    Won't idle w/o choke when cold, takes some miles for that to happen.
    #20